Getting the actual (not default) input value of a node group for a specific user
import bpy

# get the object
ob = bpy.data.objects.get("NAME")

# get the material in 1st material slot
if ob and ob.data.materials:
    mat = ob.data.materials[0]

    # get the material nodes
    nodes = mat.node_tree.nodes

    # get the instance of the node_group by name of the node (not label, name)
    protein_vr = nodes.get("ProteinVR")
    # if there are multiple instances in one material, others will likely be ProteinVR.001, ProteinVR.002, etc..

    # get the inputs if node exists
    if protein_vr:
        color = protein_vr.inputs[0].default_value
        gloss = protein_vr.inputs[1].default_value
        print(color[:])
        print(gloss)


I compiled the answer from these 2, there is more in them:


Control Cycles material nodes and material properties in Python
How to assign a new material to an object in the scene from Python?